Avinu Malkeinu from the Phish live album "Colorado '88"

Tracy Frydberg, in the Times of Israel wrote, 

The group has a passionate fan base in the Jewish community — it has been claimed that roughly one-third of the audience at every Phish concert is Jewish — and members of the tribe Mike Gordon (bass) and Jon Fishman (drums) are regarded as the core of the group. They started the band along with two other members while attending the University of Vermont in 1983.

Gordon is known for his “effortless spirituality” and the deep connection with Judaism that he brings to his performances. Originally from Newton, Massachusetts, he attended a Conservative synagogue and a Solomon Schechter day school.

It was Gordon who introduced the rest of the band to “Avinu Malkenu” (Our Father, our King) and other Jewish and Hebrew melodies. While conceding that not too many fans probably “get it” when the band plays “Avinu Malkenu,” Gordon said, in 2009, “To some, it seems blasphemous to take a holy prayer and play it in concert. I don’t sing it as a joke. It’s an acknowledgment of my heritage.” He continued,“When we play it, I can always look up and see the Jews in the audience smiling.”

https://www.timesofisrael.com/25-years-of-phishy-avinu-malkenu/